Process for producing single wall nanotubes using unsupported metal catalysts and single wall nanotubes produced according to this method

ABSTRACT

A process for producing hollow, single-walled carbon nanotubes by catalytic decomposition of one or more gaseous carbon compounds by first forming a gas phase mixture carbon feed stock gas comprising one or more gaseous carbon compounds, each having one to six carbon atoms and only H, O, N, S or Cl as hetero atoms, optionally admixed with hydrogen, and a gas phase metal containing compound which is unstable under reaction conditions for said decomposition, and which forms a metal containing catalyst which acts as a decomposition catalyst under reaction conditions; and then conducting said decomposition reaction under decomposition reaction conditions, thereby producing said nanotubes.

[0001] This application is a divisional of U.S. Ser. No. 08/910,495,filed Aug. 4, 1997, incorporated by reference herein in its entirety.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] This invention relates to a method for producing single wallcarbon nanotubes, also known as linear fullerenes, employing unsupportedmetal containing catalysts, for decomposition of a C₁ to C₆ carbonfeedstock such as carbon monoxide.

[0004] 2. Description of the Related Art

[0005] Multi-Walled Carbon Nanotubes

[0006] Multi-walled carbon nanotubes, or fibrils, are well known.Typically, carbon fibrils have a core region comprising a series ofgraphitic layers of carbon.

[0007] Since the 1970's, carbon nanotubes and fibrils have beenidentified as materials of interest for a variety of applications.Submicron graphitic fibrils belong to a class of materials sometimescalled vapor grown carbon fibers. Carbon fibrils are vermicular carbondeposits having diameters less than approximately 1.0μ. They exist in avariety of forms and have been prepared through the catalyticdecomposition of various carbon-containing gases at metal surfaces. Suchvermicular carbon deposits have been observed almost since the advent ofelectron microscopy. A good early survey and reference is found in Bakerand Harris, Chemistry and Physics of Carbon, Walker and Thrower ed.,Vol. 14, 1978, p. 83, and in Rodriguez, N., J. Mater. Research, Vol. 8,p. 3233 (1993).

[0008] Carbon fibrils were seen to originate from a metal catalystparticle which, in the presence of a hydrocarbon containing gas, becamesupersaturated in carbon. A cylindrical ordered graphitic core isextruded which immediately became coated with an outer layer ofpyrolytically deposited graphite. These fibrils with a pyrolyticovercoat typically have diameters in excess of 0.1μ. (Obelm, A. Endo,M., J. Crystal Growth, 32:335-349(1976).)

[0009] Tibbetts has described the formation of straight carbon fibersthrough pyrolysis of natural gas at temperatures of 950°-1075° C., ApplPhys. Lett. 42(8):666(18/983). The fibers are reported to grow in twostages where the fibers first lengthen catalytically and then thicken bypyrolytic deposition of carbon. Tibbetts reports that these stages are“overlapping”, and is unable to grow filaments free of pyrolyticallydeposited carbon. In addition, Tibbett's approach is commerciallyimpracticable for at least two reasons. First, initiation of fibergrowth occurs only after slow carbonization of the steel tube (typicallyabout ten hours), leading to a low overall rate of fiber production.Second, the reaction tube is consumed in the fiber forming process,making commercial scale-up difficult and expensive.

[0010] In 1983, Tennent, U.S. Pat. No. 4,663,230 succeeded in growingcylindrical ordered graphite cores, uncontaminated with pyrolyticcarbon, resulting in smaller diameter fibrils, typically 35 to 700 Å(0.0035 to 0.070μ), and an ordered “as grown” graphitic surface. Tennent'230 describes carbon fibrils free of a continuous thermal carbonovercoat and having multiple graphitic outer layers that aresubstantially parallel to the fibril axis. They may be characterized ashaving their c-axes, (the axes which are perpendicular to the tangentsof the curved layers of graphite) substantially perpendicular to theircylindrical axes, and having diameters no greater than 0.1μ and lengthto diameter ratios of at least 5.

[0011] Tennent, et al., U.S. Pat. No. 5,171,560 describes carbon fibrilsfree of thermal overcoat and having graphitic layers substantiallyparallel to the fibril axes such that the projection of said layers onsaid fibril axes extends for a distance of at least two fibrildiameters. Typically, such fibrils are substantially cylindrical,graphitic nanotubes of substantially constant diameter and comprisecylindrical graphitic sheets whose c-axes are substantiallyperpendicular to their cylindrical axis. They are substantially free ofpyrolytically deposited carbon, have a diameter less than 0.1μ and alength to diameter ratio of greater than 5.

[0012] Moy et al., U.S. Ser. No. 07/887,307 filed May 22, 1992,describes fibrils prepared as aggregates having various macroscopicmorphologies (as determined by scanning electron microscopy) includingmorphologies resembling bird nests (“BN”), combed yam (“CY”) or “opennet” (“ON”) structures.

[0013] Multi-walled carbon nanotubes of a morphology similar to thecatalytically grown fibrils described above have been grown in a hightemperature carbon arc (Iijima, Nature 354 56 1991). (Iijima alsodescribes arc-grown single-walled nanotubes having only a single layerof carbon arranged in the form of a linear Fullerene.) It is nowgenerally accepted (Weaver, Science 265 1994) that these arc-grownnanofibers have the same morphology as the earlier catalytically grownfibrils of Tennent.

[0014] Single-Walled Carbon Nanotubes

[0015] As mentioned above, the Iijima method partially results insingle-walled nanotubes, i.e., nanotubes having only a single layer ofcarbon arranged in the form of a linear Fullerene.

[0016] U.S. Pat. No. 5,424,054 to Bethune et al. describes a process forproducing single-walled carbon nanotubes by contacting carbon vapor withcobalt catalyst. The carbon vapor is produced by electric arc heating ofsolid carbon, which can be amorphous carbon, graphite, activated ordecolorizing carbon or mixtures thereof. Other techniques of carbonheating are discussed, for instance laser heating, electron beam heatingand RF induction heating.

[0017] Smalley (Guo, T., Nikoleev, P., Thess, A., Colbert, D. T., andSmally, R. E., Chem. Phys. Lett. 243: 1-12 (1995)) describes a method ofproducing single-walled carbon nanotubes wherein graphite rods and atransition metal are simultaneously vaporized by a high-temperaturelaser.

[0018] Smalley (Thess, A., Lee, R., Nikolaev, P., Dai, H., Petit, P.,Robert, J., Xu, C., Lee, Y. H., Kim, S. G., Rinzler, A. G., Colbert, D.T., Scuseria, G. E., Tonárek, D., Fischer, J. E., and Smalley, R. E.,Science, 273: 483-487 (1996)) also describes a process for production ofsingle-walled carbon nanotubes in which a graphite rod containing asmall amount of transition metal is laser vaporized in an oven at about−1200° C. Single-wall nanotubes were reported to be produced in yieldsof more than 70%.

[0019] Each of the techniques described above employs (1) solid carbonas the carbon feedstock. These techniques are inherentlydisadvantageous. Specifically, solid carbon vaporization via electricarc or laser apparatus is costly and difficult to operate on thecommercial or industrial scale.

[0020] Supported metal catalysts for formation of SWNT are also known.Smalley (Dai., H., Rinzler, A. G., Nikolaev, P., Thess, A., Colbert, D.T., and Smalley, R. E., Chem. Phys. Lett. 260: 471-475 (1996)) describessupported Co, Ni and Mo catalysts for growth of both multi-wallednanotubes and single-walled nanotubes from CO, and a proposed mechanismfor their formation.

[0021] However, supported metal catalysts are inherentlydisadvantageous, as the support is necessarily incorporated into thesingle-walled carbon nanotube formed therefrom. Single-walled nanotubescontaminated with the support material are obviously less desirablecompared to single-walled nanotubes not having such contamination.

OBJECTS OF THE INVENTION

[0022] It is thus an object of the present invention to provide a methodof producing single-walled carbon nanotubes which employs a gaseouscarbon feedstock.

[0023] It is an object of this invention to provide a method ofproducing single-walled carbon nanotubes which employs a gas phase,metal containing compound which forms a metal containing catalyst.

[0024] It is also an object of the invention to provide a method ofproducing single-walled carbon nanotubes which employs an unsupportedcatalyst.

[0025] It is a further object of this invention to provide a method ofproducing single-walled carbon nanotubes which employs a gaseous carbonfeedstock and an unsupported gas phase metal containing compound whichforms a metal containing catalyst.

SUMMARY OF THE INVENTION

[0026] The invention relates to a gas phase reaction in which a gasphase metal containing compound is introduced into a reaction mixturealso containing a gaseous carbon source. The carbon source is typicallya C₁ through C₆ compound having as hetero atoms H, O, N, S or Cl,optionally mixed with hydrogen. Carbon monoxide or carbon monoxide andhydrogen is a preferred carbon feedstock.

[0027] Increased reaction zone temperatures of approximately 400° C. to1300° C. and pressures of between ˜0 and ˜100 p.s.i.g., are believed tocause decomposition of the gas phase metal containing compound to ametal containing catalyst. Decomposition may be to the atomic metal orto a partially decomposed intermediate species. The metal containingcatalysts (1) catalyze CO decomposition and (2) catalyze SWNT formation.Thus, the invention also relates to forming SWNT via catalyticdecomposition of a carbon compound.

[0028] The invention may in some embodiments employ an aerosol techniquein which aerosols of metal containing catalysts are introduced into thereaction mixture. An advantage of an aerosol method for producing SWNTis that it will be possible to produce catalyst particles of uniformsize and scale such a method for efficient and continuous commercial orindustrial production. The previously discussed electric arc dischargeand laser deposition methods cannot economically be scaled up for suchcommercial or industrial production.

[0029] Examples of metal containing compounds useful in the inventioninclude metal carbonyls, metal acetyl acetonates, and other materialswhich under decomposition conditions can be introduced as a vapor whichdecomposes to form an unsupported metal catalyst.

[0030] Catalytically active metals include Fe, Co, Mn, Ni and Mo.Molybdenum carbonyls and Iron carbonyls are the preferred metalcontaining compounds which can be decomposed under reaction conditionsto form vapor phase catalyst. Solid forms of these metal carbonyls maybe delivered to a pretreatment zone where they are vaporized, therebybecoming the vapor phase precursor of the catalyst.

BRIEF DESCRIPTION OF THE DRAWINGS

[0031]FIG. 1 illustrates a reactor capable of producing SWNT.

[0032]FIG. 2 illustrates the vaporizer component of the reactordescribed in FIG. 1.

DESCRIPTION OF PREFERRED EMBODIMENTS

[0033] It has been found that two methods may be employed to form SWNTon unsupported catalysts. The first method is the direct injection ofvolatile catalyst. The direct injection method is described in copendingU.S. application Ser. No. 08/459,534, incorporated herein by reference.

[0034] Direct injection of volatile catalyst precursors has been foundto result in the formation of SWNT using molybdenum hexacarbonyl[Mo(CO)₆] and dicobalt octacarbonyl [Co₂(CO)₈] catalysts. Both materialsare solids at room temperature, but sublime at ambient or near-ambienttemperatures—the molybdenum compound is thermally stable to at least150°, the cobalt compound sublimes with decomposition “Organic Synthesesvia Metal Carbonyls,” Vol. 1, I. Wender and P. Pino, eds., IntersciencePublishers, New York, 1968, p. 40).

[0035] The second method uses a vaporizer to introduce the metalcontaining compound (FIG. 2).

[0036] In one preferred embodiment of the invention, the vaporizer 10,shown at FIG. 2, comprises a quartz thermowell 20 having a seal 24 about1″ from its bottom to form a second compartment. This compartment hastwo ¼″ holes 26 which are open and exposed to the reactant gases. Thecatalyst is placed into this compartment, and then vaporized at anydesired temperature using a vaporizer furnace 32. This furnace iscontrolled using a first thermocouple 22.

[0037] A metal containing compound, preferably a metal carbonyl, isvaporized at a temperature below its decomposition point, reactant gasesCO or CO/H₂ sweep the precursor into the reaction zone 34, which iscontrolled separately by a reaction zone furnace 38 and secondthermocouple 42.

[0038] Although applicants do not wish to be limited to a particulartheory of operability, it is believed that at the reactor temperature,the metal containing compound is decomposed either partially to anintermediate species or completely to metal atoms. These intermediatespecies and/or metal atoms coalesce to larger aggregate particles whichare the actual catalyst. The particle then grows to the correct size toboth catalyze the decomposition of CO and promote SWNT growth. In theapparatus of FIG. 1, the catalyst particles and the resultant carbonforms are collected on the quartz wool plug 36.

[0039] Rate of growth of the particles depends on the concentration ofthe gas phase metal containing intermediate species. This concentrationis determined by the vapor pressure (and therefore the temperature) inthe vaporizer. If the concentration is too high, particle growth is toorapid, and structures other than SWNT are grown (e.g., MWNT, amorphouscarbon, onions, etc.).

[0040] Examples 5 and 6 show many areas of SWNT along with MWNT andother carbon structures. Mo particles ranged from <1-10 nm. In Example4, mainly MWNT were formed along with other structures of carbon. Moparticles ranged from ˜1-50 nm. Presumably, the particles generated inExamples 5 and 6 were the right size to promote SWNT growth over theother forms possible. In Example 4, particle sizes favored growth ofMWNT and other forms.

EXAMPLES Example 1

[0041] In a direct injection process, the catalyst compartment wasloaded with ˜40 mg Molybdenum hexacarbonyl [Mo(CO)₆] which has beenground to ˜−100 mesh. The reactor was heated to 900° under an argonflow. Argon was then replaced with CO at atmospheric pressure at a flowof ˜0.8 SLM and the catalyst was injected.

[0042] The flow of CO was continued for 30 min. at 900° C., after whichit was replaced by argon, and the reactor furnace turned off. Aftercooling to ambient temperature, the entire contents of the reactorincluding the quartz wool plug which had been tared prior to the run,was emptied into a tared plastic bag. The quartz wool plug wasblackened, but the yield of carbon growth (wgt C/wgt catalyst) was <1.

[0043] A specimen for Transmission Electron Microscopy (TEM) wasprepared by shaking the quartz wool plug in ethanol in a glass vial andultrasounding the ethanol for ˜2 min. This procedure dispersed the blackparticles from the quartz wool. A TEM grid was prepared by evaporatingseveral drops of this dispersion onto a carbon-coated copper grid.

[0044] Examination of the grid in the TEM showed a mixture of particlesand carbon nanotubes, both MW and SW. Particles varied from ˜1-severalhundred nm and were shown to be Mo by dispersive X-ray analysis. TheMWNT ranged from ˜-4-10 nm diameter. Fishbone fibrils (10-50 nmdiameter) were also formed.

[0045] Examination of the grid also showed several areas containingSWNT. Diameters ranged between 1-2 nm. TEM estimate of the yield of SWNTwas <50% of the carbon formed.

Example 2

[0046] The procedure of Ex. 1 was used to produce a mixture of Moparticles and carbon structures including both MWNT and SWNT. Catalystcharge [Mo(CO)₆] was ˜8 mg. SWNT yield was <50% of all nanotubesproduced.

Example 3

[0047] The procedure of Example 1 was used to grow SWNT using ˜22 mgCo₂(CO)₈ as catalyst. TEM analysis revealed Co particles to be the majorcomponent. MWNT and SWNT ranging in diameter from 1-2 nm were alsoformed. Estimated yield of SWNT was <25% of the nanotubes formed.

Example 4

[0048] A simulated aerosol reactor (FIG. 1) was used to produce SWNT. Asthe catalyst sublimed in the vaporizer, the vapors were swept by thereactant gases into the reaction section where they underwent immediatethermal decomposition to Mo atoms and CO. It is theorized that the Moatoms aggregated and promoted growth of carbon structures, includingSWNT. These were caught on the quartz wool plug.

[0049] Approximately 20 mg of Mo(C)₆ was loaded into the vaporizer.Under argon at atmospheric pressure, the reactor section was heated to900° C. while keeping the vaporizer at ambient temperature. The argonstream was then changed to CO@˜8 SLM and H₂@˜0.08 SLM, and whilemaintaining 900° in the reactor, the vaporizer temperature was raised to70° C. Over the course of the run (1.5 hrs) the vaporizer temperaturerose to 80° C. due to heat from the reactor furnace. The vapor pressureof Mo(CO)₆ varied from 0.6-10 torr.

[0050] TEM specimens were made by the same procedure as Ex. 1. TENexamination showed mainly very small particles of No ranging from ˜1-10nm. Also produced were amorphous carbon structures and MWNT withdiameters ˜4 nm. SWNT with diameters ˜1.5 nm were also produced, but inlow yield.

Example 5

[0051] A procedure similar to Ex. 4 where ˜20 mg Mo(CO)₆ was loaded inthe vaporizer. With the reactor at atmospheric pressure at 900° C., thevaporizer temperature was set at 40° C. and CO was fed to the system@˜0.8 SLM. Over the course of the run (1.5 hrs) the vaporizertemperature rose to 57° C. For this temperature span, the vapor pressureof Mo(CO)₆ ranged from 0.6-2 torr.

[0052] TEM examination showed mainly Mo nanoparticles 1-10 nm indiameter along with various carbon structures. These included amorphouscarbon and MWNT with diameters of 4-10 nm. However, also produced wereSWNT with diameters varying from ˜1-3 nm. Estimated yield of SWNT was<20% of the nanotubes produced.

Example 6

[0053] Using the procedure of Exs. 4-5, ˜20 mg Mo(CO)₆ was vaporized at38-41° C. into the reactor zone which was set at 900° C. The feed gascomprised CO@0.8 SLM and H₂@0.08 SLM and was fed at atmospheric pressurefor 2.0 hrs. Vapor pressure of catalyst was nearly constant at ˜0.6torr.

[0054] TEM examination showed the presence of Mo nanoparticles, many ˜1nm diameter. The usual amorphous carbon and MWNT with diameters rangingfrom 4-10 nm were seen. However, SWNT, 1-3 nm in diameter were alsoproduced at a yield of ˜50% of the nanotubes produced.

Example 7

[0055] Examples 1-6 are summarized in Table I. Precursor was obtained asa powder from ALFA/AESAR, Research Chemicals and Materials. They wereground under an argon blanket to ˜100 mesh. CATALYST FEEDSTOCK REACTORVAPORIZER Run # PRECURSOR COMPOSITION TEMP TEMP STEM SWNT 1*  Mo(CO)₆CO-100% 900° C. NA Mix of <50% particles and MWNT/SWNT 2*  Mo(CO)₆CO-100% 900° C. NA Same as <50% above; X-ray showed no Fe 3*  Co₂(CO)₈CO-100% 900° C. NA Mostly <25% particles, some SWNT strings 4** Mo(CO)₆CO-90% 900° C. 70-80° C. Mostly trace H₂-10% particles, MWNT 5** Mo(CO)₆CO-100% 900° C. 40-57° C. Mostly <20% particles and MWNT, some SWNT 6**Mo(CO)6 CO-90% 900° C. 38-41° C. Particles, ˜50% H₂-10% few MWNT, moreSWNT

Example 8

[0056] Ferrocene (C₅H₅)₂Fe is substituted for the molybdenumhexacarbonyl in the procedure of Example 2 at an appropriate vaporpressure and temperature.

[0057] Examination of the grid in the TEM shows a mixture of particlesand carbon nanotubes, both MW and SW. Particles vary from ˜1-severalhundred nm. The MWNT ranges from ˜4-10 nm diameter.

[0058] Examination of the grid also shows several areas containing SWNT.Diameters range between 1-2 nm. TEM estimate of the yield of SWNT was<50% of the carbon formed.

Example 9

[0059] Ferrocene (C₅H₅)₂Fe is substituted for the molybdenumhexacarbonyl in the procedure of Example 6 at an appropriate vaporpressure and temperature.

[0060] Examination of the grid in the TEM shows a mixture of particlesand carbon nanotubes, both MW and SW. Particles vary from ˜1-severalhundred nm. The MWNT ranges from ˜4-10 nm diameter.

[0061] Examination of the grid also shows several areas containing SWNT.Diameters range between 1-2 nm. TEM estimate of the yield of SWNT was<50% of the carbon formed.

Example 10

[0062] Methylcyclopentadienyl manganese tricarbonyl (CH₃C₅H₄)Mn(CO)₃ issubstituted for the molybdenum hexacarbonyl in the procedure of Example2 at an appropriate vapor pressure and temperature.

[0063] Examination of the grid in the TEM shows a mixture of particlesand carbon nanotubes, both MW and SW. Particles vary from ˜1-severalhundred nm. The MWNT ranges from ˜4-10 nm diameter.

[0064] Examination of the grid also shows several areas containing SWNT.Diameters range between 1-2 nm. TEM estimate of the yield of SWNT was<50% of the carbon formed.

Example 11

[0065] Methylcyclopentadienyl manganese tricarbonyl (CH₃C₅H₄)Mn(CO)₃ issubstituted for the molybdenum hexacarbonyl in the procedure of Example6 at an appropriate vapor pressure and temperature.

[0066] Examination of the grid in the TEM shows a mixture of particlesand carbon nanotubes, both MW and SW. Particles vary from ˜1-severalhundred nm. The MWNT ranges from ˜4-10 nm diameter.

[0067] Examination of the grid also shows several areas containing SWNT.Diameters range between 1-2 nm. TEM estimate of the yield of SWNT was<50% of the carbon formed.

Example 12

[0068] Cyclopentadienyl cobalt dicarbonyl (C₅H₅)Co(CO)₂ is substitutedfor the molybdenum hexacarbonyl in the procedure of Example 2 at anappropriate vapor pressure and temperature.

[0069] Examination of the grid in the TEM shows a mixture of particlesand carbon nanotubes, both MW and SW. Particles vary from ˜1-severalhundred nm. The MWNT ranges from ˜4-10 nm diameter.

[0070] Examination of the grid also shows several areas containing SWNT.Diameters range between 1-2 nm. TEM estimate of the yield of SWNT was<50% of the carbon formed.

Example 13

[0071] Cyclopentadienyl cobalt dicarbonyl (C₅H₅) Co (CO)₂ is substitutedfor the molybdenum hexacarbonyl in the procedure of Example 6 at anappropriate vapor pressure and temperature.

[0072] Examination of the grid in the TEM shows a mixture of particlesand carbon nanotubes, both MW and SW. Particles vary from ˜1-severalhundred nm. The MWNT ranges from ˜4-10 nm diameter.

[0073] Examination of the grid also shows several areas containing SWNT.Diameters range between 1-2 nm. TEM estimate of the yield of SWNT was<50% of the carbon formed.

Example 14

[0074] Nickel dimethylglyoxime (HC₄H₆N₂0₂)Ni is substituted for themolybdenum hexacarbonyl in the procedure of Example 2 at an appropriatevapor pressure and temperature.

[0075] Examination of the grid in the TEM shows a mixture of particlesand carbon nanotubes, both MW and SW. Particles vary from ˜1-severalhundred nm. The MWNT ranges from ˜4-10 nm diameter.

[0076] Examination of the grid also shows several areas containing SWNT.Diameters range between 1-2 nm. TEM estimate of the yield of SWNT was<50% of the carbon formed.

Example 15

[0077] Nickel dimethylglyoxime (HC₄H₆N₂0₂)Ni is substituted for themolybdenum hexacarbonyl in the procedure of Example 6 at an appropriatevapor pressure and temperature.

[0078] Examination of the grid in the TEM shows a mixture of particlesand carbon nanotubes, both MW and SW. Particles vary from ˜1-severalhundred nm. The MWNT ranges from ˜4-10 nm diameter.

[0079] Examination of the grid also shows several areas containing SWNT.Diameters range between 1-2 nm. TEM estimate of the yield of SWNT was<50% of the carbon formed.

1. A process for producing hollow, single-walled carbon nanotubes bycatalytic decomposition of one or more gaseous carbon compoundscomprising the steps of: (1) forming a gas phase mixture of (a) a carbonfeed stock gas comprising one or more gaseous carbon compounds, eachsaid compound having one to six carbon atoms and only H, O, N, S or Clas hetero atoms, optionally admixed with hydrogen, and (b) a gas phasemetal containing compound which is unstable under reaction conditionsfor said decomposition, and which forms a metal containing catalystwhich acts as a decomposition catalyst under reaction conditions; (2)conducting said decomposition reaction under decomposition reactionconditions and thereby producing said nanotubes.
 2. The method definedin claim 1, wherein 50% or more of said carbon feedstock gas is carbonmonoxide.
 3. The method defined in claim 1, wherein said carbonfeedstock gas consists essentially of carbon monoxide.
 4. The methoddefined in claim 1, wherein said decomposition reaction occurs attemperatures between approximately 400° C. and approximately 1300° C. 5.The method defined in claim 1, wherein said decomposition reactionoccurs at temperatures between approximately 700° C. and approximately 1100° C.
 6. The method defined in claim 1, wherein said decompositionreaction occurs at a pressure range of approaching 0 p.s.i.g. throughapproximately 100 p.s.i.g.
 7. The method defined in claim 1, whereinsaid gas phase metal containing compound is produced by vaporizing aliquid or solid phase metal containing compound.
 8. The method definedin claim 7, wherein said metal containing compound is vaporized into aflowing stream of carbon feedstock, wherein the temperature of saidflowing stream is between approximately 400° C. and approximately 1300°C. and wherein said flowing stream is at a pressure range of approaching0 p.s.i.g. through approximately 100 p.s.i.g.
 9. The method defined inclaim 1, wherein said gas phase metal containing compound is mixed withsaid feedstock by direct injection.
 10. The method defined in claim 1,wherein said gas phase metal containing compound is in the form of anaerosol.
 11. The method defined in claim 1, wherein said gas phase metalcontaining compound is Mo(CO)₆.
 12. The method defined in claim 1,wherein said gas phase metal containing compound is Co₂(CO)₈.
 13. Themethod defined in claim 1, wherein said gas phase metal containingcompound is a volatile iron compound.
 14. The method of claim 13,wherein said volatile iron compound is ferocene.
 15. The method definedin claim 1, wherein said gas phase metal containing compound is avolatile manganese compound.
 16. The method of claim 15, wherein saidvolatile manganese compound is methylcyclopentadienyl manganesetricarbonyl.
 17. The method defined in claim 1, wherein said gas phasemetal containing compound is a volatile cobalt compound.
 18. The methodof claim 17, wherein said volatile cobalt compound is cyclopentadienylcobalt dicarbonyl.
 19. The method defined in claim 1, wherein said gasphase metal containing compound is a volatile nickel compound.
 20. Themethod of claim 19, wherein said volatile nickel compound is nickeldimethylglyoxime.
 21. The method defined in claim 1, wherein said gasphase metal containing compound is produced by subliming a solid phasemetal containing compound.
 22. The method defined in claim 1, whereinsaid gas phase metal containing compound is produced by vaporizing aliquid phase metal containing compound.
 23. Single-walled carbonnanotubes produced by catalytic decomposition of one or more gaseouscarbon compounds comprising the steps of: (1) forming a gas phasemixture of (a) a carbon feed stock gas comprising one or more gaseouscarbon compounds, each having one to six carbon atoms and only H, O, N,S or Cl as hetero atoms, optionally admixed with hydrogen, and (b) a gasphase metal containing compound which is unstable under reactionconditions for said decomposition, and which forms a metal containingcatalyst which acts as a decomposition catalyst under reactionconditions; (2) conducting said decomposition reaction underdecomposition reaction conditions and thereby producing said nanotubes.